If O2 and the proper enzymes are present what does it mean t

If O2 and the proper enzymes are present, what does it mean that pyruvate can be completely oxidized in the citric acid cycle?

Solution

Answer:

In in the presence of oxygen (aerobic), the pyruvate enters the mitochondria and is metabolized to CO2 and H2O in the citric acid cycle.

Pyruvate oxidation takes place in the mitochondrial matrix as it undergoes decarboxylation to form Acetyl CoA. Further series of oxidation steps release CO2 and reduced equivalents NADH and FADH. These high energy molecules are oxidized in the mitochondrial inner membrane as the transfer their electrons to O2 to form H2O.

But in the absence of oxygen pyruvate is decarboxylated to acetaldehyde, and acetaldehyde is reduced by NAD+ producing lactic acid. This is termed as lactic acid fermentation.